Revert "media: Remove VaapiVP8Encoder media_feature"

This reverts commit 169c1a699fcc58ee3bfb3cd30f02484794056adb.

The VP8 stream generated by using VA-API causes some issues on targets. To
disable HW VP8 encoding using VA-API via finch, we should recover this feature
variable.

TBR=beccahughes@chromium.org

Bug: 942419
Test: None
Change-Id: I5617fa55e3cb1af74b1e4fe7eaef1ed84e681c5e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1525784
Reviewed-by: Hirokazu Honda <hiroh@chromium.org>
Commit-Queue: Hirokazu Honda <hiroh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#641143}
3 files changed